1. Field of the Invention
This invention relates generally to tensile cord for endless power transmission belts, more particularly to a two-component cord useful in a belt molding process requiring a significant degree of cord extension during processing, and specifically to a belt tensile cord with a sacrificial component which “fails” during belt molding and the resulting belt.
2. Description of the Prior Art
Endless power transmission belts are well-known. Some of the common belt types include flat belts, V-belts, multi-ribbed belts, and toothed belts. Endless belts are often built by applying the various elastomeric layers, tensile members, and fabric layers onto a cylindrical mandrel, then curing or vulcanizing in a shell or bag under radially inward pressure with heat, as disclosed for example in U.S. Pat. No. 3,078,206. Building processes include upright and inverted processes. Depending on the process used, various finishing steps may be required, such as inverting, cutting, grinding, and profiling. Belt profiles may be formed by cutting or grinding after molding or by molding during vulcanization. Other building processes use an expanding mold or mandrel to press the various layered materials outward into the shell or bag, i.e., curing under radially outward pressure with heat. Such processes are disclosed for example in U.S. Pat. Appl. Pub. No. 2010/0173740 A1, U.S. Pat. No. 6,609,990 B2, JP 2004-174772 A, and JP 2004-251402 A. Molded belts may utilize a profiled mandrel or a profiled shell or bag. U.S. Pat. No. 4,184,822 discloses applying both inwardly and outwardly directed pressures against the belt body. Each of these variations has strengths and weaknesses.
In the case of molding belts with a profile formed by pressing a slab of belt materials radially outward into a rigid, profiled shell, tensile members must move with the slab material layers and stretch and also may move through the elastomeric layers which are applied to an expanding mold or mandrel under the tensile member. In some cases, particularly where the tensile member is required to stretch, the amount of expansion during the molding process may be detrimental to the tensile member. In other cases, particularly where the tensile member cannot stretch, the expansion leads to problems such as too much tensile cord movement within the expanding slab and poor cord alignment in the finished belt.
What is needed is an improved tensile member construction and method for molding endless belts on expanding molds or mandrels.